According to standards from the Cellular Telecommunications and Internet Association (CTIA) which is an international standard organization, it is a requirement for measurement of wireless performances of an antenna and a wireless device that, after a measured piece is measured at different spatial positions on a spherical surface whose center is the measured piece, a corresponding index is obtained by an integrative calculation of all the measured results. A wireless terminal can register and access the network only when its measured index satisfies the requirements. In order to ensure accuracy of the measurement, the measurement needs to be performed in an anechoic chamber, so as to eliminate noise interference from an external environment. The white paper issued by the CTIA states an extremely strict requirement for the measurement environment in the anechoic chamber. Interference caused by reflections of signals inside the anechoic chamber needs to be controlled to a certain extent, ensuring the environment inside the anechoic chamber being clear, having no reflected electromagnetic waves and being similar to an infinite vacuum, thereby ensuring the accuracy of the performance measurement of the wireless terminal.
According to a measurement provision of the CTIA, the wireless performance measurement needs to measure the performance values at the respective coordinate points of a whole spherical surface whose center is the measured piece. Taking a spherical coordinate system whose center is the measured piece as an example, the 3D wireless performance measurement of the wireless terminal requires that the wireless performance sampling measurement is performed with a step of at least 15° on θ axis and φ axis. In order to satisfy such 3D measurement requirements, there are several types of measurement systems in the related art as follows.
A first type of current measurement system is a single-antenna measurement system. A typical structure view is shown in FIGS. 1 and 2. FIG. 1 illustrates a single-antenna three-dimensional turntable system, a measured piece is placed at the axial center of a three-dimensional turntable, a measurement antenna is fixed, and the measured piece rotates about the θ axis and the φ axis via the three-dimensional turntable, achieving the wireless performance measurement of the whole spherical surface of the measured piece. FIG. 2 illustrates a single-antenna two-dimensional turntable system, the measured piece rotates around the φ axis via a two-dimensional turntable, the measurement antenna rotates about the θ axis via an annular rotating structure, such that the wireless performance measurement of the whole spherical surface of the measured piece is achieved by the combination of rotations of the turntable and the antenna. However such measurement systems have the following defects that: (1) a measuring speed is low and measuring time is long; (2) the three-dimensional turntable system in FIG. 1 and an antenna annular rotating structure in FIG. 2 will increase difficulty in design and construction of the anechoic chamber; (3) it is the most important that these mechanical devices placed inside the anechoic chamber will result in an increase of the reflection of electromagnetic waves inside the anechoic chamber, and the reflected electromagnetic waves are equal to noises for measurement, causing the microwave anechoic chamber to be not pure which is unable to simulate the infinite far vacuum environment with a ultra-low reflectivity, thereby causing the inaccuracy of the performance measurement of the wireless device.
A second type of current measurement system is a multiple-antenna measurement system. A typical structure is illustrated in FIG. 3a, two measurement antennas are arranged at positions where angles of θ are 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150° and 165° correspondingly, relative positions are fixed among the antennas, the measured piece is placed on a two-dimensional turntable, and when the turntable rotates about the φ axis at a 180° angle, the 3D wireless performance index of the measured piece can be obtained. Or, as shown in FIG. 3b or 3c, one measurement antenna is arranged at positions where angles of θ are 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150° and 165° correspondingly, the measured piece is placed on the two-dimensional turntable, and when the turntable rotates about the φ axis at a 360° angle, the 3D wireless performance index of the measured piece can be obtained. These measurement systems have a high measuring speed and a shortened measuring time, but still have the defects that: (1) when a space of the anechoic chamber is not large enough, arranging multiple antennas in the same plane will result in a relatively small distance between the antennas, i.e., isolation between the antennas is not enough and coupling interference between the adjacent antennas will bring about a measurement error; (2) since the antenna for measurement itself is a signal emission source and is a conducting medium existing inside the anechoic chamber. When an antenna for measurement is emitting the measurement signal, the other antennas can be deemed as reflection sources. Therefore, in a system of multiple measurement antennas, there is a reflection source in a small angle range of the right front of any one measurement antenna, which will increase the reflection in the anechoic chamber, resulting in inaccuracy of the measurement as well.